Lots of good demos or trailers were released or shown at E3, so I gathered a few of them below. This is not all the good ones... or even the best four. Consider this list a teaser for the library of quality video that emerged from E3.
Much of this looks to be in game footage, fairly impressive in game footage. This title looks interesting in a cult hit, not for everyone kind of way. I like games that are heavily story driven, and this appears to fit the bill. Intriguing. Gorgeous.
For me, this was one of the biggest surprises to come out of the Sony press conference. This game appears to take the concept of easy and fun level creation into whole new territory. This video is the unveiling of the title after which the developers create a new track live on stage. Fun, is the best word for this. There is nothing better than watching game developers having fun playing their own games.
The Last Guardian
You've probably seen this one already. It seems to be just about the most popular video to come out of E3. It isn't the best piece of cinematic work to be shown, not by a long shot. It is, however, a beautifully crafted piece.
Super Mario Bros Wii
If it ain't broke, don't fix it. And there is nothing broken about the good old fashioned Mario platformers. And they aren't changing a thing except the graphics. This looks to be everything a Mario platform title should be, right down to the music. When you make your Christmas list, this will be near the top.